Recoating process and recoated turbine blade

ABSTRACT

Recoating process and recoated turbine blade are disclosed. The recoating process includes providing a coated turbine blade, then removing a portion of the thermal barrier coating system to form a partially-stripped turbine blade, then applying a bond recoat to the stripped region of the partially-stripped turbine blade; and then applying a thermal barrier recoat to the bond recoat to form a recoated turbine blade. The recoated turbine blade comprises the bond coating portion abutting the bond recoat, the thermal barrier coating portion abutting the thermal barrier recoat, and the stepped configuration. The coated turbine blade has a thermal barrier coating system positioned on a substrate. The partially-stripped turbine blade has a stripped region, a bond coating portion, a thermal barrier coating portion, and a stepped configuration.

FIELD OF THE INVENTION

The present invention is directed to manufacturing processes andmanufactured components. More particularly, the present invention isdirected to recoating turbine blades and recoated turbine blades.

BACKGROUND OF THE INVENTION

Gas turbine blades are affected by operational use. Extremely hightemperatures and long cycle times result in properties that can benefitfrom repair or replacement. For example, extremely high temperatures andexposure to certain materials, such as fuel, can result in oxidation,can result in fatigue, can result in damage, or other undesirablefeatures. To reduce or eliminate such effects, turbine blades arereplaced or repaired at periodic intervals.

Replacement of turbine blades can be expensive. Removal of the turbineblades for replacement from service can result in operational downtimethat can reduce overall operational efficiency. As such, any reductionof such downtime can result in substantial improvements in overalloperational efficiency of turbine systems utilizing turbine blades.Similarly, full stripping of coatings on turbine blades can be expensivedue to time and materials expended in the stripping process and therecoating process.

Also, using more than one thermal barrier coating on a turbine blade canbe undesirable aesthetically. For example, turbine blades with multiplethermal barrier coatings may have regions that look different from otherregions. Individuals may improperly perceive that such differencesrelate to the quality or other properties of the turbine blade. Suchimproper perceptions can result in decreased use and/or sales of suchturbine blades.

A recoating process and recoated turbine blade that do not suffer fromone or more of the above drawbacks would be desirable in the art.

BRIEF DESCRIPTION OF THE INVENTION

In an exemplary embodiment, a recoating process includes providing acoated turbine blade, then removing a portion of the thermal barriercoating system to form a partially-stripped turbine blade having astripped region, then applying a bond recoat to the stripped region ofthe partially-stripped turbine blade, and then applying a thermalbarrier recoat to the bond recoat to form a recoated turbine blade. Thecoated turbine blade has a thermal barrier coating system positioned ona substrate.

In another exemplary embodiment, a recoating process includes providinga coated turbine blade having a thermal barrier coating systempositioned on a substrate, then removing a portion of the thermalbarrier coating system to form a partially-stripped turbine blade havinga stripped region, a bond coating portion, a thermal barrier coatingportion, and a stepped configuration, then applying a bond recoat to thestripped region of the partially-stripped turbine blade, and thenapplying a thermal barrier recoat to the bond recoat to form a recoatedturbine blade. The recoated turbine blade includes the bond coatingportion abutting the bond recoat, the thermal barrier coating portionabutting the thermal barrier recoat, and the stepped configuration.

In another exemplary embodiment, a recoated turbine blade includes asubstrate, a bond coat portion abutting a bond recoat, a thermal barriercoating portion abutting a thermal barrier recoat, a steppedconfiguration of the bond coating portion, the bond coating, the thermalbarrier portion, and the thermal barrier coating on the substrate. Thebond coat portion and the thermal barrier coating portion includepost-operational features.

Other features and advantages of the present invention will be apparentfrom the following more detailed description of the preferredembodiment, taken in conjunction with the accompanying drawings whichillustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of an exemplary recoating process.

FIG. 2 is a schematic view of a thermal barrier coating system of acoated turbine blade during a removing step of an exemplary recoatingprocess according to the disclosure.

FIG. 3 is a schematic view of the coated turbine blade of FIG. 2.

FIG. 4 is a schematic view of a thermal barrier coating system of acoated turbine blade during a removing step of an exemplary recoatingprocess according to the disclosure.

FIG. 5 is a schematic view of the coated turbine blade of FIG. 4.

FIG. 6 is a schematic view of a thermal barrier coating system of acoated turbine blade during a recoating step of an exemplary recoatingprocess according to the disclosure.

FIG. 7 is a schematic view of the coated turbine blade of FIG. 6.

FIG. 8 is a schematic view of a thermal barrier coating system of acoated turbine blade during a recoating step of an exemplary recoatingprocess according to the disclosure.

FIG. 9 is a schematic view of the coated turbine blade of FIG. 8.

Wherever possible, the same reference numbers will be used throughoutthe drawings to represent the same parts.

DETAILED DESCRIPTION OF THE INVENTION

Provided is an exemplary recoating process and recoated turbine blade.Embodiments of the present disclosure, for example, in comparison toprocesses and coated articles without partial stripping and partialrecoating, permit operational downtime to be reduced, permit selectiverepair and replacement of turbine blades, permit conserved use ofmaterials in recoating turbine blades, permit materials to be inspectedafter removal of a thermal barrier coating and/or bond coat prior torecoating (for example, permitting inspection of a base material),permit damage from complete stripping to be reduced or eliminated, or acombination thereof.

FIG. 1 schematically shows a recoating process 100. The recoatingprocess 100 includes providing a coated turbine blade 201 (step 102), asis further described in the embodiments shown in FIGS. 2-5, removing aportion of a thermal barrier coating system 203 (step 104), as isfurther described in the embodiments shown in FIGS. 2-5, applying a bondrecoat 601 (step 106), as is further described in the embodiments shownin FIGS. 6-7, and applying a thermal barrier recoat 801 to the bondrecoat 601 (step 108), as is further described in the embodiments shownin FIGS. 8-9.

The coated turbine blade 201 is any suitable blade, bucket, vane, or airfoil. Referring to FIG. 2, the coated turbine blade 201 has a thermalbarrier coating system 203 positioned on a substrate 205. The substrate205 is any suitable metal material, metallic material, alloy,superalloy, or combination thereof. Suitable alloys include, but are notlimited to, nickel-based alloys and cobalt-based alloys.

The thermal barrier coating system 203 is any suitable material(s)capable of providing thermal resistance for the coated turbine blade201. In one embodiment, the thermal barrier coating system 203 includesa bond coating 202 and a thermal barrier coating 204. The bond coat 202includes one or more bond coat materials, such as, MCrAlY (where M is ametal element), NiCrAlY, CoNiCrAlY, FeNiCrAlY, or a combination thereof.The thermal barrier coating 204 includes ceramics, yttria-stabilizedzirconia, gadolinium zirconate, rare earth zirconates, or a combinationthereof.

The removing of the portion of the thermal barrier coating 203 (step104) forms a partially-stripped turbine blade 209 having a strippedregion 211, for example, as is shown in FIGS. 2 and 4. As used herein,the term “partially-stripped” refers to having a portion but not all ofthe thermal barrier coating system 203 being removed. The portionincludes part or all of the thermal barrier coating 204. In oneembodiment, the portion includes part of the bond coating 202. In oneembodiment, the removing (step 104) is by a stripping method, forexample, water-jet stripping, grit-blast stripping, acid stripping, or acombination thereof. The removing (step 104) is a single-step process ora multiple-step process (for example, with an individual step forstripping the all or a portion of thermal barrier coating portion 204and an individual step for stripping a portion of the bond coating 202).In one embodiment, the removing (step 104) is performed without removalof the coated turbine blade 201 from a turbine system (not shown) orafter removal of the coated turbine blade 201, such as, a powergeneration system or a turbine engine.

The stripped region 211 extends into the partially-stripped turbineblade 209, for example, into a thermal barrier coating portion 207 ofthe partially-stripped turbine blade 209 and a bond coat portion 213 ofthe partially-stripped turbine blade 209. In one embodiment, thestripped region 211 has a stepped configuration, for example, as aplurality of cascading layers arranged in a step-like manner.

As shown in FIGS. 2-3, in one embodiment, the partially-stripped turbineblade 209 includes the bond coat portion 213 and the thermal barriercoating portion 207 prior to the applying of the bond recoat 601 (step106) (as shown if FIGS. 6-7) and the applying of the thermal barrierrecoat 801 (step 108) (as shown in FIGS. 8-9). As is shown in FIGS. 4-5,in one embodiment, the partially-stripped turbine blade 209 includes thebond coat portion 213 and is substantially devoid of the thermal barriercoating portion 207 (see FIGS. 2-3) and/or the thermal barrier coating204 of the thermal barrier coating system 203 prior to the applying ofthe bond recoat 601 (step 106) and applying of the thermal barrierrecoat 801 (step 108).

In one embodiment, the method 100 includes one or more inspection steps(not shown). The inspection steps are prior to the removing (step 104)and/or after the removing (step 104) but prior to the applying of thebond recoat 601 (step 106). The one or more inspection steps are by anysuitable inspection techniques. Suitable techniques include, but are notlimited to, non-destructive techniques and destructive techniques. Theone or more inspection steps identify regions to be removed and/orrecoated, for example, due to identifiable surface features.

The bond recoat 601 and the thermal barrier recoat 801 are applied tothe partially-stripped turbine blade 209 to predetermined regions by anysuitable processes. The bond recoat 601 includes material similar to,compatible with, or identical to the bond coating 202. The thermalbarrier recoat 801 includes material similar to, compatible with, oridentical to the thermal barrier coating 204. Suitable processes forapplying the bond recoat 601 and/or the thermal barrier recoat 801include, but are not limited to, air plasma spray, high-velocityoxy-fuel spray, suspension thermal spray, chemical vapor deposition,electron beam physical vapor deposition, physical vapor deposition,other suitable application processes, or a combination thereof.

As shown in FIGS. 6-7, the applying of the bond recoat 601 (step 106) isto the stripped region 211 of the partially-stripped turbine blade 209.In one embodiment, the applying of the bond recoat 601 (step 106)includes applying a first bond recoat to the substrate and applying asecond bond recoat to the first bond recoat. Any suitable number ofrecoat steps are used. In one embodiment, the applying of the bondrecoat 601 (step 106) is devoid of masking. In one embodiment, theapplying of the bond recoat 601 (step 106) to the partially-strippedturbine blade 209 does not apply the bond recoat 601 outside of thestripped region 211 of the partially-stripped turbine blade 209. Inanother embodiment, the applying of the bond recoat 601 (step 106) tothe partially-stripped turbine blade 209 applies the bond recoat 601outside of the stripped region 211 of the partially-stripped turbineblade 209.

As shown in FIGS. 8-9, the applying of the thermal barrier recoat 801(step 108) forms a recoated turbine blade 901. In one embodiment, theapplying of the thermal barrier recoat 801 (step 108) is devoid ofmasking. In one embodiment, the applying of the thermal barrier recoat801 (step 108) to the partially-stripped turbine blade 209 does notapply the thermal barrier recoat 801 outside of the stripped region 211of the partially-stripped turbine blade 209. In another embodiment, theapplying of the thermal barrier recoat 801 (step 108) to thepartially-stripped turbine blade 209 applies the thermal barrier recoat801 outside of the stripped region 211 of the partially-stripped turbineblade 209.

After the applying of the bond recoat 601 (step 106) and the applying ofthe thermal barrier recoat 801 (step 108), the recoated turbine blade901 is formed. In one embodiment, the recoated turbine blade 901includes the bond recoat 601 (see FIG. 8), and the bond recoat 601 abutsthe bond coating portion 213 (see FIG. 8) of the thermal barrier coatingsystem 203. In a further embodiment, the bond coating portion 213differs from the bond recoat 601 by being post-operational, therebyhaving been oxidized, heat-exposed (for example, to a temperature above1,500° F.), fuel-exposed, otherwise impacted by operational use, or acombination thereof.

In one embodiment, the recoated turbine blade 901 includes the thermalbarrier recoat 801, and the thermal barrier recoat 801 abuts the thermalbarrier coating portion 207 of the thermal barrier coating system 203.In a further embodiment, the thermal barrier coating portion 207 differsfrom the thermal barrier recoat 801 by being post-operational, therebyhaving been oxidized, heat-exposed (for example, to a temperature above1,500° F.), fuel-exposed, otherwise impacted by operational use, or acombination thereof.

The arrangement within the recoated turbine blade 901 of the bond coatportion 213, the bond recoat 601, the thermal barrier coating portion207 (if present), and the thermal barrier recoat 801 is any suitableconfiguration. Suitable configurations include, but are not limited to,a stepped configuration as is described above, an overlappingconfiguration, a tapered configuration with a blending of materialsbetween layers, having mismatched layers (for example, the bond coatportion 213 and the bond recoat 601 being slightly out of relativealignment and/or the thermal barrier coating portion 207 and the thermalbarrier recoat 801 being slightly out of relative alignment), any othersuitable configuration, or a combination thereof.

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. A recoating process, comprising: providing acoated turbine blade, the coated turbine blade having a thermal barriercoating system positioned on a substrate; then removing a portion of thethermal barrier coating system to form a partially-stripped turbineblade having a stripped region; then applying a bond recoat to thestripped region of the partially-stripped turbine blade; and thenapplying a thermal barrier recoat to the bond recoat to form a recoatedturbine blade.
 2. The recoating process of claim 1, wherein the thermalbarrier coating system includes a thermal barrier coating and a bondcoat.
 3. The recoating process of claim 1, wherein the removing is bywater-jet stripping.
 4. The recoating process of claim 1, wherein thepartially-stripped turbine blade comprises a bond coat portion and athermal barrier coating portion prior to the applying of the bond recoatand the applying of the thermal barrier recoat.
 5. The recoating processof claim 1, wherein the partially-stripped turbine blade comprises abond coat portion and is substantially devoid of a thermal barriercoating of the thermal barrier coating system prior to the applying ofthe bond recoat and applying of the thermal barrier recoat.
 6. Therecoating process of claim 1, wherein the partially-stripped turbineblade has a stepped configuration.
 7. The recoating process of claim 1,comprising inspecting the partially-stripped turbine blade prior toapplying the bond recoat.
 8. The recoating process of claim 1, whereinthe applying of the bond recoat to the partially-stripped turbine bladeincludes applying a first bond recoat to the substrate and applying asecond bond recoat to the first bond recoat.
 9. The recoating process ofclaim 1, wherein the applying of the bond recoat is devoid of masking.10. The recoating process of claim 1, wherein the applying of the bondrecoat to the partially-stripped turbine blade does not apply the bondrecoat outside of the stripped region of the partially-stripped turbineblade.
 11. The recoating process of claim 1, wherein the applying of thebond recoat to the partially-stripped turbine blade applies the bondrecoat outside of the stripped region of the partially-stripped turbineblade.
 12. The recoating process of claim 1, wherein the applying of thethermal barrier recoat is devoid of masking.
 13. The recoating processof claim 1, wherein the applying of the thermal barrier recoat to thepartially-stripped turbine blade does not apply the thermal barrierrecoat outside of the stripped region of the partially-stripped turbineblade.
 14. The recoating process of claim 1, wherein the applying of thethermal barrier recoat to the partially-stripped turbine blade appliesthe thermal barrier recoat outside of the stripped region of thepartially-stripped turbine blade.
 15. The recoating process of claim 1,wherein the recoated turbine blade comprises the bond recoat, and thebond recoat abuts a bond coating portion of the thermal barrier coatingsystem.
 16. The recoating process of claim 1, wherein the recoatedturbine blade comprises the thermal barrier recoat, and the thermalbarrier recoat abuts a thermal barrier coating portion of the thermalbarrier coating system.
 17. The recoating process of claim 1, whereinthe recoated turbine blade has a stepped configuration.
 18. Therecoating process of claim 1, wherein the removing of the portion of thethermal barrier coating system from the coated turbine blade isperformed without removal of the coated turbine blade from a turbinesystem.
 19. A recoating process, comprising: providing a coated turbineblade, the coated turbine blade having a thermal barrier coating systempositioned on a substrate; then removing a portion of the thermalbarrier coating system to form a partially-stripped turbine blade havinga stripped region, a bond coating portion, a thermal barrier coatingportion, and a stepped configuration; then applying a bond recoat to thestripped region of the partially-stripped turbine blade; and thenapplying a thermal barrier recoat to the bond recoat to form a recoatedturbine blade; wherein the recoated turbine blade comprises the bondcoating portion abutting the bond recoat, the thermal barrier coatingportion abutting the thermal barrier recoat, and the steppedconfiguration.
 20. A recoated turbine blade, comprising: a substrate; abond coat portion abutting a bond recoat; a thermal barrier coatingportion abutting a thermal barrier recoat; and a stepped configurationof the bond coating portion, the bond coating, the thermal barrierportion, and the thermal barrier coating on the substrate; wherein thebond coat portion and the thermal barrier coating portion includepost-operational features.